Emulsions and dispersions of many natural and synthetic waxes are used as additives in a variety of applications. U.S. Pat. No. 2,045,455 teaches how to prepare fine particle size emulsions of carnauba wax in water with the aid of surfactant. Since the emulsification process is practiced at temperatures greater than the melt temperature of the wax, the resultant fine particle dispersions are often referred to as "wax emulsions" rather than "wax dispersions." This distinction reflects the fact that the system was prepared by combining two immiscible liquids. However, when cooled, the wax droplets become dispersed solid particles. Wax emulsions are referred to as nonionic, anionic, or cationic, depending on the nature of the surfactant used to prepare the emulsion.
In the floor polish industry, it is desirable to use wax emulsions having both fine particle size and narrow size distribution of the dispersed wax as additives in floor polish formulations to improve the durability, buffability, scuff resistance, and slip resistance of a dried film of the end floor polish product on a floor. Fine particle wax emulsions, especially emulsions of functionalized synthetic polyolefin waxes, are common additives in floor polish formulations.
Functionalized polyolefin waxes which are easily emulsified into the particles having fine size and narrow size distribution are prepared by functionalizing the wax according to methods such as oxidation and maleation to make the wax more hydrophilic. "Functionalized polyolefin waxes" as used herein refers to either a homopolymeric or heteropolymeric polyolefin molecule which has been altered by the free radical or other type of addition or grafting of a hydrophilic side chain onto the hydrophobic polyolefin backbone, wherein the side chain group could be derived from a single molecule or an oligomer of an acid or anhydride functional species such as acrylic acid or maleic anhydride, and the like. Heteropolymeric polyolefin molecules are copolymers which typically contain one alpha-olefin copolymerized with another polyolefin, usually a minor amount, such as a copolymer of ethylene containing up to 10 weight percent of another alpha-olefin. Functionalized waxes, prepared either through air oxidation with or without a catalyst, or by reaction with acid or arthydride functional species such as acrylic acid or maleic anhydride, are easily emulsified as fine sized particles in water with the aid of surfactants. Air oxidation results in the formation of polar carboxylic acid groups covalently bound to the wax. Examples of air oxidized polyolefins and air oxidation processes are disclosed in U.S. Pat. Nos. 2,879,239; 3,519,588 and 3,329,667. Reaction with maleic anhydride, commonly called "maleation," results in the formation of hydrophilic dicarboxylic acid/anhydride groups covalently bound to the wax. Examples of maleated polyolefins are disclosed in U.S. Pat. Nos. 3,480,580 and 3,642,722. The functionality of the synthetic waxes used to prepare wax emulsions is crucial for determining end-product application performance of the emulsion.
Emulsions having the application performance properties required for use as floor polish additives or similar coating applications contain functionalized polyolefin wax typically having a molecular weight greater than 1,000. A problem commonly encountered with functionalized wax emulsions, especially emulsions of functionalized polyolefin wax having a molecular weight greater than 1,000, is undesirable yellowish-brown color. Floor polish products having a substantially colorless or water-white color are generally preferred by consumers. Even a lightly colored emulsion that merely appears dirty or dingy is considered to be colored since it is aesthetically unpleasant. Since color of individual ingredients in a formulation can affect the overall color of the end floor polish product, emulsion color is a critical criterion for marketability of a wax emulsion as a floor polish additive. Strictly controlled emulsification conditions and the addition of sodium metabisulfite, a reducing agent, are known to somewhat minimize the color of wax emulsions. However, even with strictly controlled conditions, the functionalized polyolefin wax emulsion is still colored, too highly colored for general consumer acceptance.
An approximately 25 percent solids non-ionic emulsion of AC-540, an ethylene/acrylic copolymer wax from Allied Signal, Inc., has a bluish-white translucent appearance. Yet this emulsion of an ethylene/acrylic copolymer wax does not produce a dried film having the durability, buffability, scuff resistance and slip resistance properties associated with emulsions of funstionalized polyolefin waxes.
The recipes for successfully preparing fine particle size, narrow size distribution emulsions are very well defined. Large deviations from the recipes will result in significant increases in average particle size resulting in emulsions with poor application performance properties and having limited commercial use.
U.S. Pat. No. 3,496,150 (polymaleates); U.S. Pat. No. 3,600,366 (polymaleates); U.S. Pat. No.4,959,468 (glycosides);U.S. Pat. No. 4,720,540 (thermoplastics); 5,292,864 (polyaspartic acid) and U.S. Pat. No. 4,525,580 (glyoosides) require that the colored polymer be dissolved in either an aqueous solution or an organic solution prior to contact with an aqueous bleaching agent. These disclosed processes for reducing the color of non-polyolefin polymers require that the polymer be in a single-phase system, such as a molten polymer or a polymer dissolved in an inert solvent, prior to the bleaching process. None of these processes are suitable for reducing the color of a two-phase wax emulsion.
In light of the above, it would be very desirable to be able to reduce the color of emulsions of functionalized polyolefin waxes without reducing their application performance properties.